It seems that this web site:
http://www.military-steel-helmets-and-decals.com
Is selling extinguisher decals.
They are water slip but be advised I have spoken with the guy (Brantley) and these are ink jet printed on off the shelf water slip paper.
The quality is nowhere near as good as lacquer ink decals and they guy is hiding the fact that they are simply ink jet printed. I emailed him pretending to be in need of some decals for RC airplanes and after the third email he let slip what he was doing.... well, once he realized that I was calling him on his printing process.
For $5 its a good deal. Don't expect them to last long (inkjet ink) DOES FADE unless you have a professional printer (ever see those company logo's ads that cover a car or truck? They are printed via inkjet technology, but the ink is nowhere near the same. Although most full coverage vinyl signs are silk screened, some lower end places just run it through an inkjet).
For $5 you could buy one and spray them with a clear coat... that will make it last a little longer... but the quality is just not the same a lacquer ink water slip decal.. there is a reason he is selling them so cheap.